Brain injury (part 1) – mild concussion and the cycle helmet myth

Have you have heard of US champion snowboarder Kevin Pearce? I’d say over the next few weeks we’ll all hear more about him and the movie “The Crash Reel” which follows Kevin after he suffers a debilitating brain injury while training for the Olympics.

#LoveYourBrain is the outreach campaign born from The Crash Reel and Kevin Pearce’s inspiring story. The campaign focuses on the need for everyone to recognise the importance of their brain and to LOVE IT.

Your Brain Health is happily jumping on board this one! In honour of #LOVEYOURBRAIN I’m writing a series of blog posts about brain injury – what happens inside the injured brain, what brain injury tells us about the brain’s capacity for repair, and in a few weeks, one of the hottest topics in neuroscience – neuroplasticity.

First up, this week I’m going to take a look at mild traumatic brain injury, more commonly known as concussion.

What is concussion?

Traumatic brain injury (TBI) is the leading cause of death and disability in children and adults and is involved in nearly half of all trauma deaths worldwide. This is not a small problem.

Concussion is a defined as a sudden-onset, transient alteration of consciousness due to a combination of functional and structural brain disturbances following a physical impact transmitted to the brain. Simply put, the brain doesn’t work as it should because of damage to brain cells (neurons).

Concussion is common. In Australia, the frequency of hospitalisation from sports-related concussion is on the increase (even when the numbers of people taking part in sport are accounted for). For example, in the Australian Football League (AFL), concussion is estimated to occur at a rate of approximately seven injuries per team per season.

That figure is CRAZY?!

Other sports such as motor sports, equestrian activities, rugby union and league, cycling and roller sports make up the rest.

What are the symptoms of concussion?

It’s commonly thought that concussion is related to loss of consciousness, but that only occurs in about 10%–20% of cases.

Most concussions resolve within a few days to weeks, but in some cases the symptoms can last for much longer.

It is too much detail to get into here – but here is a link to Sports Medicine Australia’s concussion first aid recommendations.

Concussion is a mild form of traumatic brain injury

This means that both neurons and the fine network of blood vessels of the brain become damaged.

The type of injury that is most damaging to the brain is not just the knock to the head (a focal brain injury), but rather the twisting or rotating of the brain inside the skull. The rotation causes mechanical stretching or ‘shearing’ of axons (a diffuse axonal injury) which in turn triggers a neurochemical cascade that leads to further cellular damage (both of neurons and their supporting cells called gila), dysfunction and maybe neuronal death. Small blood vessels also tear causing minor bleeding, oxygen deprivation, swelling and blood-brain barrier damage.

In a later post I’ll talk a bit more about the medium- to longer-term response of neurons, glia and the immune system to this damage.

Long term effects of repeated concussion

Several studies have examined the association between head injury and risk of dementia in late-life. Head injury has been shown to increase the risk of cognitive decline, dementia and Alzheimer’s disease.

Even mild brain injury results in the same brain pathology as seen in Alzheimer’s disease, and this is especially so in cases of repeated concussion.

Professor Andrew Kaye, director of the department of neurosurgery at The Royal Melbourne Hospital thinks there are enormous potential for ongoing problems caused by concussion in sport.

It’s not just one or two concussions, and not just whether injured players should go back on the ground, but more about whether sub-concussive head injuries could have a cumulative effect.

How do we promote the engagement of youth in these sports and, at the same time, ensure that they are safe from concussion?

You’d think this answer to Professors Kaye’s question would be simple, right?

Do helmets prevent concussion and brain injury?

When I was skiing last winter I had this debate with a snowboarder. See that image at the top of the blog post. That’s me wearing a ski helmet. He told there was no evidence to show that it would prevent brain injury – so why bother wearing one?

Always one for checking out the evidence and statistics I thought I’d take a look into it and of course there are two sides to the story.

Recent research on new Canadian legislation mandating helmet use for all cyclists has found helmets have minimal effect on serious head injuries.

Ben Goldacre, doctor, epidemiologist (and one of my superheros) wrote in response to the Canadian paper and the contentious issue of cycle helmet laws in the BMJ. He says,

Supporters of helmets often tell vivid stories about someone they knew, or heard of, who was apparently saved from severe head injury by a helmet. Risks and benefits may be exaggerated or discounted depending on the emotional response to the idea of a helmet.

If you’re interested Goldacre’s paper is well worth reading as it delves into public health policy, risk, the behaviour of people who do wear helmets, and all the complex layers of politics, culture, and psychology surrounding the issue.

Should I bother wearing a cycle helmet or not?

To me there is no decision. Maybe helmets don’t protect against severe head injury in the population at large (the case is still out), but they DO provide protection against mild, or moderate injury. And repeated mild brain injury or concussion IS catastrophic.

So, I’m well and truly on board with Kevin Pearce and #LOVEYOURBRAIN campaign.

What an interesting article.
I do hope you remember that both you and your sister both wore bike helmets when you were younger.
And I recall both of you had the need for tme on at least one occasion each.
You both fell or were forced off your bikes by motorists and managed to hit the deck and cause some reasonable damage to your bike helmets